Contacting solids and fluids



May 4, 1954 2,677,604

K. J. NELSON CONTACTING SOLIDS AND FLUIDS Filed Dec. 14, 1946 sSheets-Sheet 1 PRODUCTS TO COAL FEED INLET RECOVERY FEED STANDPIP BEDLEVEL NTROLLER 47 FLUIDIZING GAS INLET 2 FLuID 2o 40 vEssEL 47 CHAR 3DISCHARGE sLIDE VALVE AIR PREHEATER F l G. 1

KARL J. NELSON INVENTOR BY ATTORNEY 7 9 T '7 g l5 MAKE GAS y 1954 K. J.NELSON 2,677,604

CONTACTING SOLIDS AND FLUIDS Filed Dec. 14, 1946 3 Sheets-Sheet 2PRODUCTS TO COAL FEED INLET RECOVERY FEED STANDPIPE LEVEL i H CONTROLLERFLUIDIZING k GASYINLET s.- 45

F LOW CONTROLLER GHAR DISCHARGE sums ems OR i g COAL INLET VA LVE 60RECIRCULATED TEMPERATURE CONTROLL ER Karl J.- Nelson iNVENTOR sv yywATTORNEY y 4, 1954 K. J. NELSON 2,677,604

CONTACTING SOLIDS AND FLUIDS Filed Dec. 14, 1946 3 Sheets-Sheet 3 COALGAS I5 RECIRCULATED 9 7 17- FLOW CONTROLLER 87 PREHEATER as FLUID HEATERBED O L 89 LEVEL CONTROLLER 29 so I PRODUCTS TO 97 RECOVERY 83 1 .1 2FLUID 82 CARBONIZER ,L 99% 2Q 93 -23 T i k 95 z j COAL FEED w A 67 CHARWl/ 69 DISCHARGE SLIDE 7 VALVE 74 75 F CONTROLLER 73 |9 FlG.-3

KARL J. NELSON INVENTOR BY ATTORNEY Patented May 4, 1954 CONTACTINGSOLIDS AND FLUIDS Karl J. Nelson, Cranford, N. J., assignor to StandardOil Development Company, a corporation of Delaware Application December14, 1946, Serial No. 716,408

Claims. 1

The present invention is concerned with the control of operatingconditions in processes involving the contact of fluidized finelydivided solids with fluids. More particularly, the present inventionrelates to the treatment of carbonaceous materials such as all types ofcoal, lignites, cellulosic materials including lignin, oil shale, tarsands, coke, oil coke, heavy residues, asphalts and the like intovaluable volatile products such as coal gas, water gas, producer gas,light oils, tars and chemicals by preheating, carbonization and/orgasification, in dense turbulent beds of finely divided solids fluidizedby an upwardly streaming gas.

The application of the so-called fluid solids technique to thepreheating, carbonization and/ or gasification of carbonaceous solids iswell known in the art. In these processes, finely divided carbonaceoussolids such as coal or coke having a fluidizable particle size of, sayabout, 50-400 mesh are fed to a treating or conversion zone such as apreheating, carbonization or gasification zone wherein they aremaintained at treating temperatures in the form of a dense turbulentfluidized bed of finely divided solids forming a well defined upperlevel.

The heat required for the treatment is usually supplied either byblowing superheated steam, hot product gas or flue gas upwardly throughthe "eating zone; or by burning a portion of the combustibleconstituents of the charge with the aid of an oxidizing gas such as airand/or oxygen passed upwardly through the treating zone; or by burningsolid carbonaceous conversion residue in a separate heater andrecirculating hot solid combustion residue to the treating zone.

Fluidization is accomplished by controlling the linear velocity ofeither the process and heating gases or of an extraneous fluidizing gasintroduced into the treating zone, at about 0.3- ft. per second.Volatile products are Withdrawn overhead while solid residues arerecovered from the upwardly flowing vapors and gases and/or from afluidized solids stream leaving the treating zone in a downwarddirection under the pseudo-hydrostatic pressure of the dense fluidizedbed.

The advantages of this procedure over fixed bed operation are great innumber and importance. The temperature throughout the fluidized beds isperfectly uniform and may be easily controlled over the wide range offrom, say. about 700 to about 2500" F. The yields of volatile and solidconversion products may be substantially improved and readily variedwith respect to product qualities and relative product amounts bysuitable variations of temperature, pressure and/or reaction time. Theprocesses may be made fully continuous and may be applied to any type ofcarbonaceous charge. There is highest flexibility with respect to thetype of heating employed. Investment and operating cost is likewise morefavorable as compared With fixed bed operation.

However, in order to secure these advantages, it is important tomaintain constant operating conditions, particularly of temperature andcontact time, in the treating zones. This invention relates, in its morespecific aspects, to the control of systems of the treatment ofcarbonaceous solids employing the fluid solids technique atsubstantially constant operating conditions.

it is, therefore, the principal object of my invention to provide meansfor controlling the operating conditions of processes involving thecontact of fluidized solids with gases.

Another object of my invention is to provide improved means forconverting carbonaceous materials into more valuable volatile products.

A more specific object of my invention is to provide means for treatingcarbonaceous solids in the form of a dense turbulent fluidized mass offinely divided solids at constant operating conditions.

A still further object of my invention is to provide means forcontrolling the operating conditions of processes for convertingcarbonaceous solids into volatile products employing the fluid solidstechnique.

Another object of my invention is to provide improved apparatus forcarrying out processes of the type specified.

Other and further objects and advantages of my invention will appearhereinafter.

In accordance with the present invention, the temperature and contacttime of processes involving the contact of a fluidized solid with a gasare maintained at the desired values by maintaining a constant heatsupply While varying the solids feed as a function of temperaturevariations and the solids withdrawal as a function of the fluid :bedlevel which determine the bed holdup, i. e. the weight of solids in thereaction zone at any given time. Hold-up on the other hand is one of themajor factors determining solids residence time.

When applying my invention to the treatment of fluidized carbonaceoussolids at constant operating conditions, the heat supply is maintainedconstant by feeding a constant amount of oxygen to the treating zone togenerate a constant amount of heat of combustion; or by supplying aconstant amount of sensible heat of gases or solids to the treating zoneby feeding constant amounts of heating gases or solids preheated to aconstant temperature. The temperature of the treating zone is keptconstant by decreasing or increasing the amount of fresh carbonaceoussolids supplied to the treating zone as a function of temperaturefluctuations. The bed hold-up and thus the solid residence time at anygiven solids feed rate are kept constant by allowing the height of thefluidized carbonaceous solids bed to control the speed of withdrawal oftreated solids from the fluidized bed.

In cases in which heat is supplied as sensible heat of preheated gasesor solids, the temperature of the gas or solids preheater may becontrolled by the desired temperature of the heat carrier as a furthermeans of excluding independent variables.

It will be understood that the installation of automatic controls or"the type specified makes permanent supervision of the process conditionssuperfluous.

Having set forth the general nature and objects, my invention will bebest understood from the more detailed description hereinafter in whichreference will be made to the accompanying drawing wherein:

Figure 1 represents a unit for the conversion of carbonaceous solidsinto volatile products using partial oxidation within the conversionzone as a means of supplying heat of conversion;

Figure 2 represents a similar unit using the sensible heat of anexternally heated gas as a means of heat supply; and

Figure 3 illustrates a conversion unit using the sensible heat ofexternally heated solids as a means of heat supply.

Referring now to Figure 1, the numeral 28 designates a fluid solidsconversion zone which hereinafter will be referred to as a carbonizerfor the carbonization or" coal although other treatments of carbonaceousolids and other materials may be carried out therein in a substantiallyanalogous manner.

In operation, finely divided carbonization coal having a particle sizebetween about 10 and 4-.00 mesh, preferably between 50 and 200 mesh,although larger sizes up to about A; to inch diameter may be used, issupplied to carbonizer 28 from line i by any suitable means known in theart such as a standpipe 3 aerated through taps 5 with small amounts of afluidizing gas such a air, flue gas, product gas, steam or the like. Theflow if solids through feed pipe 3' is regulated by a slide valve 6.

An oxidizing gas such as air and/ or oxygen is supplied from line i bycompressor Si via a knockout and surge drum H pressure controlled at E3and through a flow controller [5 and, if desired, a preheater IT, toline l9 which leads to the lower conical portion of carbonizer 2B.

The oxidizing gas enters carbonization zone 23 of carbonizer 29 througha distributing grid 2!. The amount of oxygen supplied should besufiicient to cause a limited combustion of combustible coalconstituents adequate to generate at least the major portion of the heatrequired for carbonization in zone 23. About 0.1 to 0.8 lb. of air or acorresponding amount of oxygen per pound of carbonization coal isgenerally sufiicient to establish carbonization temperatures of about8G0 to 1400" F. within zone 23.

The finely divided coal and coke in zone 23 is fluidized by the fluegases and volatile carbonization products to form a dense turbulent massof solids resembling a boiling liquid and forming a well defined upperlevel (L20). Linear gas velocities within the approximate limits ofabout 0.3 and 10 it. per second are generally suitable to establish afluidized mass of an apparent density of about 5-60 lbs. per cu. ft. inzone 23 at the particle sizes mentioned above.

Volatile carbonization products such as coal gas, light oils, tars, etc.pass overhead from level (L20) through a conventional gas-solidsseparator such as cyclone 25. In order to prevent tar condensation andplugging in cyclone 25 an eiiicient heat transfer from zone 23 or anadditional heat supply should be effected, preferably by any of themeans disclosed and claimed in the copending applications, Serial No.700,884, filed October 2, 1946, now Patent No. 2,549,117, granted April17, 1951 and Serial No. 702,020, filed Octoher 8, 1946, now Patent No.2,537,153, granted September 1, 1951. Carbonaceous solids finesseparated in cyclone 25 may be returned to zone 23 through pipe 21.

Product vapors and gases, substantially free of solids are passedthrough line 29 to a conventional product recovery system (not shown).Carbonized coal consisting substantially of coke is withdrawn downwardlyunder the pseudohydrostatic pressure of the fluidized bed in zone asthrough bottom drawoff pipe 3! which may be aerated through taps 33. Thespeed of solids withdrawal through pipe 3| is regulated by a slide valve35.

In order to operate the process at constant conditions of temperature,pressure and contact time, the system shown in Figure 1 is provided witha control system which operates in accordance with my invention as willbe presently described.

Pressure controller i3, flow controller l5 and preheater ll are presetto establish an oxidizing gas supply or" a constant pressure of, say,about 10500 lbs. per sq. in., preferably about 15-60 lbs. per sq. in., aconstant amount per unit of time depending on the s ze and desiredoutput of carbonizer 28, corresponding to about 1.3 to 10 s. c. f. ofair r lb. of coal to be carbonized; and a constant preheatingtemperature of about 200-1000 F. In this manner, carbonizer 20 issupplied with a constant amount of oxygen at constant conditions whichwill liberate a constant quantity of heat by combustion because the fuelsupply in carbonizer 28 is present in a very large excess. The pressurein carbonizer 20 is likewise kept constant within narrow limits by thecontrolled back pressure on the by-product recovery system (not shown).

A temperature-responsive device such as a thermocouple 49 arrangedwithin zone 23 acts on con ventional, actuating means 53 which operateslide valve 6. These actuating means are so designed and respond tothermocouple 49 in such a manner that the normal opening of slide valve6' is reduced when the temperature in zone 23 tends to fall below thedesired level and increased if the temperature tends to rise above thedesired temperature. In this manner the feed rate of the fresh charge ofrelatively low temperature is used to keep the carbonization temperatureconstant within a narrow range of say about 5--15 F.

The bed hold-up and thus the solids residence time of the coal in zone23 is controlled by the height of level (L20). In order to maintainlevel (L20) and thus the bed hold-up and solids residence time in zone23 constant, a bed level indicator 55 is provided which acts byconventional means on electrical mechanical hydraulic and/or pneumaticactuating means 41 which operate slide valve 35. When level (L) risesabove its normal level, valve 35 is opened beyond its normal opening.When level (L20) drops below its normal level, valve 35 is closedbeneath its normal opening. The normal valve opening is restored uponlevel (L20) reaching its normal position.

It will be appreciated that the control means shown in the drawingpermit a fully automatic control of the process at substantiallyconstant operating conditions.

Referring now to Figure 2, I have shown there in a system similar tothat illustrated by Figure 1 wherein the sensible heat of a highlypreheated as is used to supply the heat required for carbonization. Likereference numerals designate like elements of the systems of Figures 1and 2.

The operation of the system of Figur 2 is substantially the same as thatdescribed with reference to Figure 1 except for the character, amount,and temperature of the gas supplied through line l9.

This gas may be superheated steam, make or flue gas, or the like andwill be referred to as make gas by way of example. Such make gasrecovered from the volatile carbonization products is passed from line 7by a blower or compressor 3 via flow controller Hi to a tube furnaceheater i? wherein it is preheated to a temperature about 109-800 F.higher than the desired temperature in carbonization zone 23, dependingon the amount of gas supplied to said zone per unit of coal rocessed.Fuel and air are supplied to heater ll from lines 50 and 52,respectively, provided with control valves 56 and 56. In general, about5 to 140 s. c. f. of gas preheated in heater ll to about 950 to 1600 F.is sufiicient per lb. of coal to be carbonized to establish acarbonization temperature of about 850-1400 F. in zone 23.

The amount of make gas fed is kept constant by flow controller l5. Inorder to maintain the temperature of the heat-carrying gas constant atthe desired level, a temperature-responsive means such as a thermocouple58 is located in line l9 at a point close to its entrance intocarbonizer 2i Thermocouple 58 acts on conventional actuating means 50and 62 which operate fuel control valve 54 and air control valve 56 in amanner known per se to increase or decrease the rate of combustion inheater I! when the temperature of the gas in pipe l9 drops below orrises above the normal desired temperature. In this manner, the heatsupply to zone 23 is kept constant and automatic process control maytake place as outlined in connection with Figure 1.

Referring now to Figure 3, the system shown therein will likewise beexplained with reference to the carbonization of coal heat forcarbonization being supplied as sensible heat of solids highly preheatedin an external heater. The reference numerals of Figures 1 and 2 havebeen used to designate like or corresponding elements.

The coal feeding means 3 is shown to be a screw-conveyor actuated by anelectric motor E3 rather than a standpipe controlled by a slide valve.Line [9 now merely serves to supply a gas for the fluidization of zone23 at a predetermined constant rate and temperature, controlled by flowcontroller i5 and preheater IT. The fiuidizing gas which may be madegas, steam,

or flue gas preheated to a constant temperature within the range of say200 to 1200 F. in heater ll is preferably introduced through adistributing cone 65 covered by grid 2|. This arrangement permits apercolation of finely divided coke downwardly around cone 65 into theconical bottom portion of carbonizer 20 for purposes ex plained below.The superficial linear velocity of the fluidizing gas may be kept withinthe approximate limits of 0.3 to 10 ft. per second.

The automatic control of temperature, pressure and contact time in zone23 is substantially the same as that outlined in connection with Figures1 and 2. However, the means for providing a constant heat supply and forcontrolling the temperature of the heat carrying agent are different aswill be forthwith explained.

The heat required for carbonization is generated by the combustion ofchar from carbonizer 2c in a separate heater 8!] as follows. Finely divided char entering the conical bottom portion of carbonizer 2E! fromzone 23 around cone 65 is stripped of entrained gas and by-products andmaintained in a readily flowing state by introducing small amounts of astripping gas through one or more taps 61. This char passes downwardlythrough pipe 69 provided with a control valve H into line E3. Air issupplied from line ill by compressor '12, via pressure-regulated surgeand knockout drum M and flow controller it to line 73 to form with thechar from line 69 a dilute suspension of solids-in-gas. This suspensionpasses under the pressure of the air in line it and thepseudo-hydrostatic pressure of the solids column in pipe 69, throughline '53 into heater 80.

The amount of air supplied through line it should be constant andsufiicient to make available the oxygen required to generate heat ofcombustion adequate to support the carbonization reaction. About 0.7 to12 s. c. f. of air per pound of coal to be carbonized is normallysuitable to maintain a heater temperature about 100- 300 F. higher thanthe temperature desired in zone 25. This amount of air is based on achar supply of about 0.8 to 20 lbs., through line is, per lb. of coal tobe carbonized. The air enters heater through a distributing grid 82 at alinear velocity of about 0.3 to 10 ft. per second to convert incooperation with the gases produced, the solids in combustion zone 83into a dense fluidized mass having an upper level (Lao) similar to thefluidized mass in zone 23.

Flue gases are withdrawn overhead from level (Lao), passed through acyclone separator and vented through line 8?, if desired, after heatexchange with fiuidizing gas in preheater i1 Solids separated in cyclone85 may be returned to zone 83 through line 89.

Solid combustion residue is withdrawn down-- wardly from a point abovegrid 82 through line which may be a standpipe similar to stand pipe 3 ofFigures 1 and 2, aerated through one or more taps Q3. The flow of solidsthrough pipe 9! is controlled by slide valve 95. Solid combustionresidue from pipe 9| enters zone 23 substantially at the temperature ofcombustion zone 83 in amounts of about 0.8 to 20 lbs. of residue per lb.of coal carbonized to supply the heat required in zone 23.

In order to maintain the amount of heat sup-- plied to zone 23 at aconstant level, I make the char supply through line [3 dependent on theheater temperature and the supply of hot combustion residue to zone 23dependent on the bed level of the solids in heater 80.

For this purpose, a temperature responsive means such as a thermocouple91 is arranged in zone 83 to act on conventional actuating means 99which operate valve H of line 69. When the temperature in zone 83 risesabove the desired normal level, the opening of valve H is increasedabove the normal width and vice versa. Thus, when maintaining a constantsupply of air the temperature of combustion zone 83 is kept constant.

On the other hand, a bed level indicator liil acts on conventionalactuating means Hi3 which operate valve 95 in line 9| so as to reduceits opening below normal when level (L80) in zone 83 drops below normaland vice versa.

t will be appreciated that these automatic controls regulating theheater operation secure the supply of a constant amount of heat to zone23 and cooperate with the control means of carbonizer 20 to establishconstant operating conditions and fully automatic control of the entireprocess.

While I have referred in the above examples to the carbonization 01carbonizable solids, other reactions may be carried out in zone 23 in asubstantially analogous manner. For example, zone 23 may serve as apreheating zone by merely reducing the preheating and operatingtemperatures below the temperature of beginning carbonization and/orplasticization of the feed. Water gas may be produced in zone 23 byraising the heating temperature to a gasification level. such asl600-2500 F. and supplying adequate amounts of steam through line [3 tosupport the gasification reaction. Other analogous applications of myinvention, which will occur to those skilled in the art, are within thescope of the invention.

While the foregoing description and exemplary operations have served toillustrate specific applications and results of my invention, othermodifications obvious to those skilled in the art are within the scopeof the invention. Only such limitations should be imposed on theinvention as are indicated in the appended claims.

I claim:

1. The method of contacting holds with a dense turbulent mass of finelydivided solids having a ell defined upper level in a treating zone atconstant conditions of treating temperature and solids residence time,which comprises passing said fluids upwardly through said mass,supplying a substantially constant amount of finely divided solidsheated to a temperature not below treating temperature at asubstantially constant temperature to said mass to supply a constantamount of heat thereto, said amount of heat being sufficient to maintainsaid temperature, feeding a stream of fresh finely divided solids havinga temperature substantially below said treating temperature to saidmass, said heated finely divided solids being supplied independently ofsaid fresh solids, withdrawing a stream of finely divided treated solidsfrom said mass, changing the rate of flow of said stream of fresh solidsin the same direction as said treating temperature changes so as tomaintain said treating temperature substantially constant and changingthe rate of flow of said treated solids in the same direction as theheight of said mass changes so as to maintain said level substantiallyconstant.

2. The process of claim 1 wherein said fresh solids are carbonizable andsaid treating conditions are carbonization conditions.

3. The process of claim 1 wherein said treating conditions arepreheating conditions.

a. The process of claim 1 wherein said fresh solids are carbonaceous,said gas comprises steam and said treating conditions are conducive tothe formation of water gas.

5. The process of treating carbonaceous solids in the form of a denseturbulent mass of finely divided solids fluidized by an upwardly flowinggas to form a well defined upper level in a treating zone at constantconditions of treating temperature and solids residence time, whichcomprises supplying to said mass a finely divided heat-carrying solidcombustion residue heated to a constant temperature not below saidtreating temperature, at a substantially constant rate and in amountssufiicient to maintain said temperaturc, feeding a stream of freshfinely divided carbonaceous material having a temperature substantiallybelow said treating temperature to said mass, said heat-carrying solidsbeing supplied independently of said fresh material, withdrawing astream of finely divided treated solids from said mass, changing therate of flow of said stream of fresh material in the same direction assaid treating temperature changes so as to maintain said treatingtemperature constant, changing the rate of fiow or" said stream oftreated solids in the same direction as the height of said mass changesso as to maintain said level constant, passing at least a portion ofsaid withdrawn stream of solids to a separate fluid solids combustionzone operated at a combustion temperature higher than said treatingtemperature, supplying a constant amount of air of substantially constartemperature to said combustion zone, passing highly heated solids fromsaid combustion zone to said treating zone to supply said heat-carryingsolids, changing the flow rate of said portion passed to said combustionzone in the same direction as said combustion temperature changes so asto maintain said combustion temperature constant and changing the flowrate of said heatcarrying solids passed from said combustion zone tosaid treating zone in the same direction as the bed height of thefluidized solids in the combustion zone changes so as to maintain saidlastnamed bed height constant.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,899,887 Thiele Feb. 28, 1933 1,984,380 Odell Dec. 18, 19342,399,050 Martin Apr. 23, 1946 2,438,728 Tyson Mar. 30, 1948 2,480,670Peck Aug. 30, 1949 2,482,187 Johnson Sept. 20, 1949 2,534,051 NelsonDec. 12, 1950 FOREIGN PATENTS Number Country Date 301,975 Great BritainDec. 13, 1928

1. THE METHOD OF CONTACTING FLUIDS WITH A DENSE TURBULENT MASS OF FINELYDIVIDED SOLIDS HAVING A WELL DEFINED UPPER LEVEL IN A TREATING ZONE ATCONSTANT CONDITIONS OF TREATING TEMPERATURE AND SOLIDS RESIDENCE TIME,WHICH COMPRISES PASSING SAID FLUIDS UPWARDLY THROUGH SAID MASS,SUPPLYING A SUBSTANTIALLY CONSTANT AMOUNT OF FINELY DIVIDED SOLIDSHEATED TO A TEMPERATURE NOT BELOW SAID TREATING TEMPERATURE AT ASUBSTANTIALLY CONSTANT TEMPERATURE TO SAID MASS TO SUPPLY A CONSTANTAMOUNT OF HEAT THERETO, SAID AMOUNT OF HEAT BEING SUFFICIENT TO MAINTAINSAID TEMPERATURE, FEEDING A STREAM OF FRESH FINELY DIVIDED SOLIDS HAVINGA TEMPERATURE SUBSTANTIALLY BELOW SAID TREATING TEMPERATURE TO SAIDMASS, SAID HEATED FINELY DIVIDED SOLIDS BEING SUPPLIED INDEPENDENTLY OFSAID FRESH SOLIDS, WITHDRAWING A STREAM OF FINELY DIVIDED TREATED SOLIDSFROM SAID MASS, CHANGING THE RATE OF FLOW OF SAID STREAM OF FRESH SOLIDSIN THE SAME DIRECTION AS SAID TREATING TEMPERATURE CHANGES SO AS TOMAINTAIN SAID TREATING TEMPERATURE SUBSTANTIALLY CONSTANT AND CHANGINGTHE RATE OF FLOW OF SAID TREATED SOLIDS IN THE SAME DIRECTION AS THEHEIGHT OF SAID MASS CHANGES SO AS TO MAINTAIN SAID LEVEL SUBSTANTIALLYCONSTANT.
 4. THE PROCESS OF CLAIM 1 WHEREIN SAID FRESH SOLIDS ARECARBONACEOUS, SAID GAS COMPRISES STEAM AND SAID TREATING CONDITIONS ARECONDUCIVE TO THE FORMATION OF WATER GAS.